For various reasons as will be understood in the art, network configurations may use Layer 2 (L2) and/or Layer 3 (L3) overlays on top of an Internet Protocol (IP) network. In addition, there is often a requirement for a maximum loss duration on the order of tens of milliseconds when a host moves locations within a network. This requirement cannot be easily met by a distributed system that requires multiple nodes to be updated upon a move. The only realistic way to achieve the required convergence, is the ability to do a temporary local repair at the old location away from which the host moved. At this time, the repair is applied to packets/frames that incorrectly arrive at the old host location, which redirects/re-encapsulates them toward the new host location.
For an L3 overlay carrying IP payload such a redirect is risk free, as even if nodes (transiently) have the wrong information, and a redirection loop is formed the packet will not loop forever. In particular, the time-to-live (TTL) field of the payload IP packet will decrement on every node performing a re-encapsulation and will eventually decrement to zero resulting in the packet being discarded (even if such discarding is a relatively slow process).
For an L2 overlay carrying L2 payload on the other hand, there is no hop-count or TTL in the typical L2 frame header, such as Ethernet, so if a loop is formed the packet will loop forever until the loop is broken by control plane activity. Traditional Ethernet networks use the Spanning Tree Protocol (STP) to prevent such loops from occurring, but overlay networks like virtual extensible local area network (VXLAN) do not run STP. Instead, they prevent loops by split-horizon techniques, where a node will not re-encapsulate a frame that was received over the overlay to another node on the overlay. However, the use of split-horizon prevents the redirection/re-encapsulation required in order to achieve the fast convergence via a local repair.